The present invention relates to a folding baby carriage which cannot become unexpectedly folded during running. Generally, folding baby carriages are very convenient when utilizing other transportation facilities; they are widely used. It is necessary that folding baby carriages do not become folded unexpectedly during running, even if stones or the like collide with the wheels of the carriages. On the other hand, if the folding baby carriage is provided with a special locking device as conventional ones sometimes are, there is a problem that the folding or opening operation of the baby carriage becomes difficult or troublesome.